Block-encoded video, such as video encoded using techniques compatible with the Moving Picture Experts Group (MPEG) (e.g., MPEG-2, ISO/IEC 13818, also ITU-T Rec. H.262 (2002); and/or MPEG-4, ISO/IEC 14496 also ITU-T Rec. H.264 (2003)), may suffer from discontinuities at block boundaries particularly when encoded at low bit rates where large quantization errors may occur. Such discontinuities may appear in the reconstructed video frames as blocking artifacts (e.g., visible block edges, mosaic patterns, tiling effects, etc) particularly in image regions that are smooth.
Deblocking filters implementing methods such as variable length filtering and/or edge protection may reduce the magnitude of blocking artifacts to a visually-acceptable level. However, some techniques for reducing blocking artifacts do not adequately distinguish real edges in an image frame from artifact edges. Resources may be expended on filtering artificial edges (i.e., blocking artifacts) that are unlikely to be visually detectable.